JavaScript Array and Object Methods

What are Objects in JavaScript?

Objects in JavaScript, just as in many other programming languages, can be compared to objects in real life. In JavaScript, an object is a standalone entity, with properties and type. Compare it with a cup, for example. A cup is an object, with properties.

A cup has a color, a design, weight, a material it is made of, etc. The same way, JavaScript objects can have properties, which define their characteristics.

const myHonda = {
  color: "red",
  wheels: 4,
  engine: { cylinders: 4, size: 2.2 },
};

Here, we created myHonda object with color, wheels, and engine properties.

Now, we will look at some object basics and its manipulation methods.

Return array of values from an Object: Object.values()

const coffee = {
    roast: 'dark',
    type: 'black',
    price: 3.0,
}

const coffeeStat = Object.values(coffee);

//coffeeStat will return ['dark','black',3.0]

Return array of keys from an Object: Object.keys()

const coffee = {
    roast: 'dark',
    type: 'black',
    price: 3.0,
}

const coffeeKeys = Object.keys(coffee);

//coffeeKey will return ['roast','type','price']

Return an array of keys+values: Object.entries()

const coffee = {
    roast: 'dark',
    type: 'black',
    price: 3.0,
}

const entries = Object.entries(coffee);

//entries will return [['roast','dark'],['type','black'],['price',3.0]]

Merging Object with Spread:

const firstArray = [1, 2, 3, 4];
const secondArray = [5, 6, 7, 8];

const combined = [...firstArray, ...secondArray];
// combined will be equal to [1, 2, 3, 4, 5, 6, 7, 8]

What are Arrays?

Create a new array based on the condition of a given array: .filter()

Example

Create an array of coffee that’s not over $4

const coffees = [3.2, 5.6, 1.2, 5.2, 2.2, 6.3];
const cheapCoffees = coffees.filter( coffee => coffee < 4);// cheapCoffees will be equal to [3.2, 1.2, 2.2]

Create a new array by manipulating the values of a given array: .map()

Example

Create an array that adds $ to the beginning of each price of coffee.

const coffees = [3.2, 5.6, 1.2, 5.2, 2.2, 6.3];
const coffeePrice = coffees.map( coffee => '$' + coffee);
// coffeePrice will be equal to [$3.2, $5.6, $1.2, $5.2, $2.2, $6.3]

Add up the integers in an array (sum): .reduce()

Example

Output the sum of the coffee

const coffees = [3.2, 5.6, 1.2, 5.2, 2.2, 6.3];
const total = coffees.reduce((accumulator, currentValue) => accumulator + currentValue);
// total will be equal to 23.7

Check if any item in an array passes the condition. return boolean. .some()

Example

check if there is a coffee price of 1.2 in an array

const coffees = [3.2, 5.6, 1.2, 5.2, 2.2, 6.3];
const containsPrice = coffees.some(coffee => coffee === 1.2);
// containsPrice will return true

Check if all items in an array pass the condition. return boolean. .every()

Example

check if all coffee price exceeds a dollar.

const coffees = [3.2, 5.6, 1.2, 5.2, 2.2, 6.3];
const allCoffee = coffees.every(coffee => coffee > 1.0);
// allCoffee will return true

Check if an array contains a certain value. It’s similar to .some(), but instead of checking a condition, it looks for a specific value.

Example

check if the coffee price of 6.3 is in the array

const coffees = [3.2, 5.6, 1.2, 5.2, 2.2, 6.3];
const coffeePrice = coffees.includes(6.3);
// coffeePrice will return true

References:

1. Useful Javascript Array and Object Methods
2. JavaScript reference
3. Objects: the basics
4. https://medium.com/infancyit/javascript-object-manipulation-5d1145cf06ef#:~:text=JavaScript%20is%20designed%20on%20a%20simple%20object%2Dbased%20paradigm.,and%20value%20can%20be%20anything.